1. Field of the Invention
The present invention relates to ultracentrifuges used in biology, biophysics, medicine and in other branches of science of engineering and, more particularly, it relates to a centrifuge drive.
2. Description of the Prior Art
One of the essential problems encountered in designing a centrifuge is the development of a stable, simple and reliable, particularly with regard to repairability, design of its drive.
Commonly known in the art is an ultracentrifuge drive comprising a casing with a stator inside and two end brackets whose bearings support the rotor shaft of the electric motor. Connected rigidly with the rotor shaft is a flexible shaft installed rotatably in a damping device. The drive casing is provided with spaces and passages for the circulating coolant. In this drive the bearings of the rotor shaft are installed in different end brackets which adversely affects the coaxially of the construction. Another disadvantage lies in that the bearings are pressed into the end brackets which prevents interchangeability of both the bearings proper and of their end brackets. Besides, the disassembly of the drive is a time- and labour-consuming operation. Still another disadvantage of the known design resides in the presence of thermal resistance existing between the surface of the motor stator and the circulating coolant. Therefore, the stator surface is cooled with a low efficiency. And, finally, the given design has no provision for cooling the damping device.
Another prior art centrifuge drive (U.S. Pat. No. 4322030) comprises a casing accommodating a stator and a rotor whose shaft is mounted in an angular bearing and is rigidly linked with a flexible shaft fixed rotatably in the damping device, the casing being provided with passages for the circulating coolant and lubricant.
The fast drive is located in a vacuum and its rotor can be taken out of the casing complete with the flexible shaft which facilitates repairs.
However, since the bearings are installed in separate elements of the casing, this ensures strict coaxiality in the casing. Besides, replacement of said elements calls either for precision manufacture of said bearing-fastening elements, or an overall replacement of the casing together with said elements. On the other hand, even a slight axial misalignment of bearings raises the vibration level thereby impairing the reliability of the centrifuge drive. Another disadvantage of the prior art centrifuge drive is the absence of cooling of the damping device which impairs its operating conditions especially during prolonged service.
Still another disadvantage of the prior art drive consists in the presence of thermal resistance between the surface of the drive stator and the circulating coolant. Even with the high heat conduction of the material of the casing, the stator will be cooled insufficiently because the entire drive operates in a vacuum. The same reason is responsible for poor cooling of the rotor and damping device.